Wednesday, 28 December 2016

PiWars 2017 - Manual challenges.

Its been a busy few months since I was accepted as a competitor for PiWars 2017, unfortunately very little of that time has been spent on PiWars itself. Work has been especially busy, culminating in a sudden business trip to Taiwan where I had access to shops with all the connectors, cables and components I'd need for a robot, but with no idea what I needed yet!

So in this post I've decided to jot down my ideas for the various manual challenges, as most of them have similar requirements, and its considerably easier to manually control a robot compared to telling it to deal with things itself.

My general approach will be similar to last PiWars, a four wheeled vehicle with tank style driving, controlled via a joystick, but with some improvements. Whilst I had the option on my previous robot to change the motors and wheels it ended up being too fiddly to do on the day and led to my robot being defeated by the 'humps' at the start of the obstacle course due to still being on small wheels. So this is an aspect I want to review and improve upon this time.

As the exact details of the obstacle course won't be known until the day itself I have to make some assumptions about what will be required based on previous events. I would expect certain parts of the PiWars 2015 course to be reused (especially the rotating table) with a few new elements added. As such I'll be needing a setup with good ground clearance and fine controls. A high top speed won't help much here, with the marble obstacle from last year requiring the robot to drive slowly in order not to dislodge any and occur a time penalty.

All the above is subject to change of course, the marbles may be swapped out with a gravel pit and I'll be wanting chunkier wheels to cope with that.

Having gotten to the final of Pi Noon last time (with a lucky win or two I must admit) there's probably not much to change here. I'm tempted by the mecanum wheels that Triangula was sporting last year, but I would need quite a lot of practise to be good at using them, something I've never ended up having much time for in previous events!

Skittles was a little hit and miss last time, with my robot knocking down more skittles during the practice run than it did in the official attempts. Due to time issues I ended up just pushing the ball for PiWars 2015 which, unsurprisingly, proved to be very unreliable.

Possibly approaches to it this year could be a motorised launching system (a spinning wheel or two to get the ball up to speed), a catapult type system (pulling back and releasing an elastic band), a spring loaded system or maybe something that picks up the ball and rolls it. In theory anything that can propel the ball forwards in a straight line should work out okay for skittles, whereas the next challenge potentially requires a finer degree of control.

A new challenge for PiWars 2017 is golf, and apparently a slightly deranged variant of the game. As such its a bit of an unknown, with only the details of the challenge to base things on. The game is just a single hole (No 18 hole courses here!) and the robot is only allowed to push or hit the ball to get it around the obstacles. What those obstacles are we don't know (sand pits?) and whether its better to hit or push the ball won't be known until the day itself.

The traditional approach would favour having a mechanism that can 'hit' (or propel) the ball forwards at different speeds, allowing the robot to progress through the course, changing directions to move around obstacles and eventually reach the hole. However this does sound like quite a complicated approach, as each time you need to judge how far to hit the ball, chase it with the robot, line up the next shot etc.

A simpler approach maybe to push the ball the entire way, potentially lowering a cup over the top of it to ensure the ball doesn't get away from the robot, leaving you to just drive to the hole and drop it in. This, of course, assumes the course is flat and there is enough space between obstacles for the robot to drive through. If not the ball could escape and you'd be stuck trying to capture it again.

So that's my current thoughts on the manual challenges, next up will be the autonomous ones!